Facebook is really easy to use. That is, until you get into the developer tools. I find these tools to be incredibly confusing and poorly linked to each other.
So, the other day I needed to find my Facebook ID for an application that I was working on. And I realized, I had no idea what that was. Facebook, of course, was of little help.
A simple Google search, however, brought me to http://findmyfacebookid.com/ . This website was exactly what I needed. All you need to do is put your Facebook URL into the search box, and it will spit out your Facebook ID.